Abstract
This study examines the relationships between kerosene pump frequency, in-flight particle temperature and velocity, phase composition, porosity, roughness, and mechanical properties of HVOF-sprayed WC–12Co coatings. In the primary series, the pump frequency was varied from 30 to 37 Hz, while the nominal oxygen settings, carrier-gas flow rate, spray distance, and robot program remained constant. Between the boundary conditions, the mean particle temperature increased from 1685 to 1719 °C and the mean velocity from 681 to 754 m/s. The W2C/WC ratio increased from 0.0160 to 0.0341. Porosity decreased from 2.62% for F30 to 1.95% and 1.88% for F33 and F35, respectively, before increasing to 2.45% for F37. F35 exhibited the highest mean hardness and indentation modulus; however, pairwise comparisons did not identify significant hardness differences among F33, F35, and F37. In an additional series at 30–34–34–37 Hz, the coatings deposited at the intermediate frequency also had lower mean porosity than those deposited at the boundary frequencies. These results associate the combined changes in particle thermal and kinetic conditions with coating densification and mechanical response at intermediate spraying conditions.